The present invention relates generally to fluid circulation pumps. More particularly, it relates to fluid pumps suitable for use in connection with a nuclear reactor.
Spool-type fluid pumps have traditionally been used to move fluids as part of a chemical process, or to propel sub-sea vessels. Spool-type fluid pumps generally comprise two concentric cylinders. The outer cylinder contains the pump stator, while the inner cylinder contains the pump rotor. Impeller(s) are connected to a central hub and extend out to, and connect with, the inner cylinder. When power is supplied to the stator, an electromagnetic field is generated, causing the inner cylinder, including the impeller(s), to rotate.
The inner and outer cylinders are sealed or xe2x80x9ccannedxe2x80x9d in order to prevent fluid from coming in contact with the internals of the rotor and stator. Generally, there exists a small gap between the inner and outer cylinders, which can be filled with water in order to cool the rotor and stator. The water has been provided through a fluid circulation channel that may be disposed in the central hub and run through one of the impellers to a gap between the cylinders. Alternatively, the fluid circulation channel may begin at one end of the pump as a gap between the inner cylinder and the outer cylinder. The water flows through the channel between the inner cylinder and the outer cylinder and exits through a gap between the inner cylinder and the outer cylinder at the other end of the pump. The traditional designs are inadequate in terms of cooling when the pump is used in connection with high temperature applications.
Nuclear reactors have traditionally utilized shaft seal pumps or canned motor pumps, that are connected between the steam generator and the reactor vessel by large coolant piping for circulating coolant from the reactor vessel through the steam generator. The steam generator and pump are located outside the reactor vessel, with the reactor coolant being circulated by the pumps through the reactor vessel, steam generator, piping system and through the pumps. The pump casing becomes part of the primary pressure boundary surface.
The shaft seal pump used for nuclear reactor coolant pumping is traditionally a vertical single stage pump having a motor driver connected by a coupling. The motor is either an air cooled or water cooled squirrel cage induction design, but is located outside of the pump casing. A shaft seal assembly seals the reactor coolant inside the pump.
Because radioactive fluid is being moved through the pump and the coolant piping, any leaks in the shaft seal, pump casing, vessel opening and closure should be avoided. Therefore, it is desirable to provide a nuclear reactor configuration that decreases the likelihood of such leaks.
In one embodiment the fluid pump comprises a sealed annular stator having a generally cylindrical passage extending therethrough, with the stator having energizing means for electrically connecting a plurality of stator windings to a source of electrical power. The fluid pump further comprises an impeller assembly rotatably mounted in the generally cylindrical passage in the housing. The impeller assembly comprises an impeller and a sealed rotor mounted around the perimeter of the impeller and positioned inside the stator to form an electric motor, the operation of which rotates the impeller to produce a pressurized flow of fluid through the generally cylindrical passage in the housing. The fluid pump further comprises at least one radial bearing mounted between the impeller assembly and the housing, a hub centrally positioned in the generally cylindrical passage in the housing and secured to the housing by at least one impeller blade, the impeller assembly rotatably supported on the hub, and insulation material disposed within the stator, the insulation material consisting essentially of mica, glass and ceramics.
In another embodiment, the fluid pump comprises a sealed annular stator having a generally cylindrical passage extending therethrough, with the stator-having energizing means for electrically connecting a plurality of stator windings to a source of electrical power. The fluid pump further comprises an impeller assembly rotatably mounted in the generally cylindrical passage in the housing. The impeller assembly comprises an impeller and a sealed rotor mounted around the perimeter of the impeller and positioned inside the stator to form an electric motor, the operation of which rotates the impeller to produce a pressurized flow of fluid through the generally cylindrical passage in the housing. The fluid pump further comprises at least one radial bearing mounted between the impeller assembly and the housing, a hub centrally positioned in the generally cylindrical passage in the housing and secured to the housing by at least one impeller blade, and cooling tubes having an inlet downstream of the impeller and an outlet upstream of the impeller, the cooling tubes disposed at least partially within the stator.
In another embodiment, the nuclear reactor comprises a reactor vessel, nuclear fuel, a plurality of control rods, reactor coolant, at least one steam generator, and at least one reactor coolant pump, wherein the nuclear fuel, the control rods, the reactor coolant and the reactor coolant pump are all located inside the reactor vessel.